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Liquid-conducting electrical household applianceLiquid-conducting electrical household appliance description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070163626, Liquid-conducting electrical household appliance. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to an electrical household appliance comprising a chamber which is at least partially filled with liquid during operation of the appliance and a pump driven by a motor for sucking out liquid from the chamber. Such a household appliance can in particular be a dishwasher or a washing machine and the pump is a discharge pump which sucks out cleaning liquor from a lower part of the chamber in order to spray it on to items to be cleaned which are located in the chamber or to pump it away from the chamber. [0002] If the quantity of washing liquor in the chamber is too low, unsatisfactory cleaning results are achieved because the pump sucks in air in addition to the cleaning liquor and an adequate liquor pressure for satisfactory cleaning results is not achieved at the pressure output of the pump. If, on the other hand, the quantity of liquor in the chamber is larger than is necessary, this results in uneconomic operation on the one hand because of the unnecessarily high water costs and on the other hand because the energy requirement for heating the liquor to the desired cleaning temperature increases together with the quantity of liquor. It is therefore important to match the quantity of liquor exactly to the requirement. This can be achieved, for example, by installing a flow meter in an inlet pipe of the chamber which monitors the amount of fresh water taken in and shuts off a valve in the inlet pipe when a predetermined amount of water is reached. Such a flow meter is not only costly but it is also unable to match the amount of water taken-in in individual cases to the degree of contamination of the items to be cleaned with the machine. If a dishwasher, for example is loaded with severely contaminated dishes, proteins contained in the contamination can result in substantial foaming of the rinsing liquor with the result that not only rinsing liquor but also foam is sucked out by the pump. In exactly the same way as sucked-in air when the liquor level is too low, the foam prevents the build-up of a sufficiently high pressure at the pump output and thus a satisfactory cleaning effect. The foaming can be counteracted by letting in a larger quantity of water but this is uneconomical if it happens during every cleaning process, as described above. Conventional dishwashers therefore frequently have program buttons which allow a user to select different washing programs with different water usage according to the degree of contamination of the loaded dishes. Since the assessment of the degree of contamination by the user is to a certain extent subjective, and it is easy to forget to use the appropriate selection button, optimal efficiency cannot be ensured in this way. [0003] With a machine which is able to individually adapt the amount of water used in each case to the degree of contamination of the items to be cleaned, it would not only be possible to increase user friendliness but also to improve the economic efficiency. [0004] If the cleaning liquor is severely contaminated, this can result in a blockage of the pump or its upstream or downstream pipes which blocks the movement of the pump and therefore the motor. Since in such a case, the motor performs no mechanical work, the entire electrical power taken up thereby, which is possibly increased under such circumstances compared with normal operation, is converted into heat which can result in damage or even destruction of the motor. In principle, it is possible to detect such a blockage using a flow meter of the aforesaid type connected in series with the pump but as stated above, such a sensor is costly and it takes up valuable space in the household appliance. [0005] It is the object of the invention to provide an electrical household appliance of the type defined initially which allows the recognition of disturbances in the fluid flow through the pump using simple, inexpensive and reliable means. [0006] The object is achieved by an electrical household appliance having the features of claim 1. [0007] The invention assumes that a fixed relationship exists between the rotational speed and power of the motor, which is substantially determined by the design of the pump and the flow resistances of pipes through which the pump pumps the liquid. Upward or downward deviations from this relationship which can be determined empirically for a given model of household appliance respectively indicate different types of disturbances. For this reason the household appliance has a monitoring device for detecting the rotational speed and power of the motor, for comparing detected values of rotational speed and power with a predefined characteristic and for signalling an exceptional state if the comparison indicates that the detected values deviate significantly from the characteristic. [0008] If the detected power of the motor for a detected rotational speed is significantly lower than a power to be expected for the detected rotational speed using the predefined characteristic, this is an indication that not only liquid but also foam or air are being pumped. Both problems can be remedied by letting additional water into the chamber of the household appliance. For this reason, the household appliance has an inlet valve for admitting liquid into the chamber and a control device which is set up to open the inlet valve when the monitoring device signals a first exceptional state in which the detected power for the detected rotational speed is significantly lower than a power which is to expected for this rotational speed with reference to the characteristic. [0009] Equivalent to a detected power which is lower than that to be expected for the detected rotational speed using this characteristic is the detection of a rotational speed which is significantly higher than that to be expected using this characteristic for a given power. [0010] The household appliance can have a plurality of circulating paths via which the liquid circulated by the pump can be guided as desired, as described in Wegner, Electrical Household Appliances/Engineering and Service, Verlag Huthig & Pflaum 2000, for a washing machine. Since different circulating paths of this type have different flow resistances, the monitoring device is appropriately set up to use a specific characteristic for the respectively selected circulating path as the basis for comparison depending on the selected circulating path. [0011] It can also be appropriate to use different characteristics as the basis for comparison in the course of the working sequence of the household appliance. Thus, for example, in an initial phase of the working sequence of a dishwasher, a first characteristic can be taken as the basis assuming that at this time a deviation from the characteristic indicates that the pump is sucking in air as a result of an inadequate amount of liquor. In a later phase of the sequence, in particular if the amount of liquor has already been adjusted using the afore-mentioned first characteristic, a deviating characteristic of power and rotational speed can be used to detect foam formation. [0012] If the monitoring device signals a second exceptional state in which the power detected together with a detected rotational speed is significantly higher than is to be expected using the predefined characteristic, this can indicate a fault in the movement of the motor. In this case, it can be provided that the control device interrupts the working sequence of the household appliance to protect the motor or that it delivers a warning signal to request a user to take countermeasures to protect the motor. [0013] It is known per se to connect a filter for collecting impurities in the pump liquid before the inlet to the pump. An elevated power of the motor in relation to the rotational speed can also indicate a blockage of this filter so that an appropriate reaction of the control device to an elevated power detected by the monitoring device can be to control or instigate cleaning, in particular a flushing of this filter. [0014] A synchronous motor is preferably used as the motor in the household appliance according to the invention. Such a motor allows its rotational speed to be detected comparatively simply merely by monitoring the time behaviour of the electromotive force in the windings of the motor, i.e. the currents or voltages occurring at the motor so that expensive and space-consuming sensors are not required on the motor or the pump to determine the rotational speed. [0015] The armature of the motor is preferably located in a pump chamber of the pump. Such an armature, also known as a wet armature can dispense with a seal on the shaft between the armature and the pump where friction losses could occur to a degree which cannot be accurately monitored. This design of armature thus allows the mechanical power delivered by the pump to be determined particularly accurately from the electrical power taken up by the motor. [0016] Further features and advantages of the invention are obtained from the following description of exemplary embodiments with reference to the appended figures. [0017] In the figures: [0018] FIG. 1 shows a schematic section through a dishwasher according to the invention; [0019] FIG. 2 is a block diagram of the motor of the circulating pump of the dishwasher from FIG. 1 as well as its supply electronics; [0020] FIG. 3 shows example of the rotational speed-power characteristics forming the basis of the motor controller; and [0021] FIG. 4 shows a section through an assembly which combines the pump, the motor and the supply electronics. [0022] FIG. 1 shows a schematic section through a dishwasher comprising a washing chamber 1 in which baskets 2 and 3 are located in a usual manner such that they can be pulled out guided on rails. Located in a recess at the bottom of the washing chamber 1 is a washing water filter 4 through which a pump 5, which is explained in further detail subsequently with reference to FIG. 2, sucks washing water to supply rotatably mounted nozzle arms 6, 7 which are mounted respectively underneath the baskets 2, 3 to spray the items to be washed contained therein. A directional valve 8 located between the output of the pump 5 and the nozzle arm 6 or 7 is periodically switched by a microcontroller 31 (see FIG. 2) between the position shown in the figure in which lower nozzle arm 7 is supplied with washing water via a pipe 13 and a position in which the upper nozzle arm 6 is supplied via a pipe 12. [0023] Naturally, in a simpler configuration the valve 8 could also be omitted so that both nozzle arms 6, 7 are supplied at the same time. In this case, however, both pipes 12, 13 must be filled with water at the same time during operation of the nozzle arms 6, 7 so that the overall amount of water required for washing is greater than that during alternating operation of the spray arms 6, 7 using the valve 8. [0024] An inlet valve 10 also controlled by the microcontroller 31 is used for the controlled admission of fresh water into the washing chamber via a fresh water pipe 11. Continue reading about Liquid-conducting electrical household appliance... Full patent description for Liquid-conducting electrical household appliance Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Liquid-conducting electrical household appliance patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Liquid-conducting electrical household appliance or other areas of interest. ### Previous Patent Application: Method for forming a photoresist pattern Next Patent Application: Method for diafiltration of a product and device for carrying out this method Industry Class: Cleaning and liquid contact with solids ### FreshPatents.com Support Thank you for viewing the Liquid-conducting electrical household appliance patent info. IP-related news and info Results in 1.16293 seconds Other interesting Feshpatents.com categories: Novartis , Pfizer , Philips , Polaroid , Procter & Gamble , 174 |
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